1. Technical Field
The present invention relates to a liquid crystal display apparatus, and in particular, to a method and device for supplying data to a data driver for a liquid crystal display panel.
2. Prior Art
The resolution of the display region of a liquid crystal display apparatus has recently been increasing; compared to conventional video graphic arrays (VGA) that have allowed display with 640.times.480 pixels, super VGAs (SVGAs) or extended graphic arrays (XGAs) allow display with 800.times.600 or 1024.times.768 pixels. With such a high resolution display, a source driver for supplying data to each pixel has a large operation frequency or is very expensive, or a new source driver must be developed. A higher operation frequency also prevents EMC regulations from being met. Furthermore, since an increase in resolution requires the size of the display region to be increased, the length of a signal transmission path and the impedance are accordingly increased, thereby preventing accurate signals from being transmitted at a high speed.
Attempts have been made to reduce the operation frequency of the source driver. For example, Japanese Patent Unexamined Published Application No. 5-100632 discloses a method for writing a data signal to four memories and then supplying the data from these memories to four source drivers. Since four source drivers drive a single liquid crystal display panel, the operation frequency of a single source driver is one-fourth of a conventional source driver. The capacity of each of these memories, however, must be twice the number of those pixels for which a source driver is responsible when it drives a single line. That is, a single memory stores data corresponding to those pixels contained in a single line for which the source driver is responsible. This data is subsequently read from the memory, while the data in the next line is written to that memory. A similar method is described in Japanese Patent Unexamined Published Application No. 5-181431.
Japanese Patent Unexamined Published Application No. 5-232898 also describes a method for providing four memories for two data drive circuits and using a switch to switch these memories to obtain similar effects.
Although the above conventional techniques indeed enable the operation frequency of the source driver to be reduced, the resultant increase in the number of source drivers may require the total capacities of the memories to be increased, or the control circuit may be complicated due to the use of the switch in the case of the method described in Japanese Patent Unexamined Published Application No. 5-232898.